1. Field of the Invention
This invention relates to a closure for a container of the kind having a pouring aperture and a venting aperture in one end of the container, and more particularly but not exclusively to a closure for a can containing liquid under pressure, such as a carbonated drink or beer.
2. Description of the Prior Art
British Patent Specification No. 1,389,351 describes a can of this kind provided with an opening device moulded from a plastics material so as to have a resilient aperture or lip portion defining a pouring aperture and a smaller venting aperture aligned with the container openings, the lip portion being airtightly connected to the can end; a resilient removable portion connected to the lip portion by a hinge between adjacent ends of said portions, the removable portion carrying plugs on its undersurface which are attached in an airtight but rupturable manner to the edges of the apertures in the lip portion; and a pull tab normally located adjacent the hinge and connected to said removable portion by two legs which encircle the removable portion and are connected to its further or outer end, adjacent the periphery of the can end. In order to open the device the user lifts the pull tab and the legs transmit the force exerted on the pull tab to the outer end of the removable portion so as to rupture the plugs from the pouring aperture and the vent aperture in turn. Continued pulling thus opens the pouring aperture and then the vent aperture and the hinge allows the removable portion to be extended away from the apertures to facilitate drinking or pouring, while keeping it attached ready for reclosure by fitting the plugs on the removable portion into the apertures.
A major problem with the closure arrangement described in British Patent Specification No. 1,389,351 is that first opening is at a point near the periphery of the can end. At this point there is a risk that, if the can is slightly tilted, the liquid will be in contact with the point of first opening so that on opening gaseous pressure in the headspace will force the liquid out of the pouring aperture, putting the user at risk of getting wet and losing some of his drink. British Patent Specification No. 1,389,351 also describes an alternative opening device which comprises a lip portion defining a pouring aperture and a venting aperture; a removable portion carrying plugs on its underside closing both apertures; and a pull ring extending from the removable portion near the venting aperture. This alternative opening device gives the benefit of first opening the vent aperture near the centre of the can end, so permitting dry venting of the can before opening the pouring aperture, but no connection is provided between the lip portion and the removable portion, presumably because a hinge between the adjacent ends of these portions at their outer ends would obstruct drinking or pouring. The loose reclosure portion may easily be lost and may then become an environmental nuisance.